Add general Runge-Kutta class - Add a general Runge-Kutta class which time integrates the solution based on coefficients obtained from a Butcher tableau - Add butcher tableau which returns coefficents for the specified Runge-Kutta method - Remove RungKutta4proper, since obsolete

% Calculates M so that the stepsize m/M is as close to n/M as possible
function M = equal_step_size(n,N,m)
    M = round((m*(N-1)+n)/n);
end